132 



MORPHOLOGY OF SPERMATOPHYTES 



A 



FIG. 93. G-netum Gnemon: 

 .4, a young embryo at the 

 tip of a suspensor and im- 

 bedded in endosperm ; B, 

 a germinating seed, the 

 root and stem tips having 

 escaped, and the foot re- 

 maining within the seed 

 coat. After BOWER. 



In the germination of the oospore, and in the structure of 

 the female gametophyte, there is evidence that Tumboa and 

 Gnetum are allied forms, the latter hav- 

 ing proceeded further in the reduction 

 of its gametophyte preceding fertiliza- 

 tion. It is also evident that Ephedra 

 must be associated with them as the least 

 modified form, its gametophyte retain- 

 ing the character of those in other Gym- 

 nosperms, while the germination of its 

 oospore is fairly transitional between 

 Conifers on the one hand and Tumboa 

 and Gnetum on the other. There is free 

 nuclear division in the oospore, as in 

 Conifers, but the cells organized in con- 

 nection with them remain independent 

 and behave as do the oospores of Tumboa 

 and Gnetum. It should be remarked, 

 also, that the number of free cells de- 

 veloped within the oospore of Ephe- 

 dra may be reduced to two, and that any further reduction 

 would probably result in causing the whole oospore to behave as 

 do these of Tumboa and Gnetum. If Ephedra be associated 

 with Tumboa and Gnetum, as seems reasonable, there is equally 

 weighty evidence for regarding it as the group of Gnetales most 

 nearly related to the Conifers, for its female gametophyte and 

 the early stages in the germination of its oospore are identical 

 with those in Conifers. 



LITERATUEE CITED 



1. HOOKER, J. D. On Welwitschia, a new genus of Gnetaceae. 



Trans. Linn. Soc. London 24: 1-48. pis. 1-14. 1863. 



2. EICHLER, A. W. Ueber Welwitschia mirabilis, etc. Flora 47: 



459-464, 473-479, 489-496, 508-510, 513-520. 1863. 



3. STRASBURGER, E. Die Coniferen und die Gnetaceen. 1872. 



4. BECCARI, O. Delia organogenia del fieri feminei del Gnetum 



Gnemon L. Nuovo Giorn. Bot. Ital. 7: 91-99. 1877. 



5. STRASBURGER, E. Die Angiospermen und die Gymnospermen. 



1879. 



6. BOWER, F. O. On the Germination and Histology of the Seed- 



lings of Welwitschia mirabilis. Quart. Jour. Micr. Sci. 21 : 

 15-30. pis. 3-4. 1881. 



